1. Field of the Invention
The present invention relates to a laser processing machine that performs laser-processing on a wafer such as a semiconductor wafer or the like along streets formed on thereon.
2. Description of the Related Art
In a semiconductor device fabrication process, the front surface of an almost-disklike semiconductor wafer is sectioned into a plurality of areas by predetermined dividing lines called streets arranged in a lattice pattern. Devices such as ICs, LSIs or the like are formed in the areas thus sectioned. The semiconductor wafer is cut along the streets to divide the areas formed with the devices therein for fabricating the individual devices. An optical device wafer in which a light-receiving element such as a photo diode or the like or a light-emitting element such as a laser diode or the like are stacked on the front surface of a sapphire substrate or of a silicon carbide (SiC) substrate is also cut along streets and divided into individual optical devices such as light-emitting diodes, laser diodes or the like, which are widely used in electric equipment.
A method is proposed of irradiating a wafer along streets formed thereon with a laser beam to form laser processing grooves and rupturing the wafer along the laser processing grooves. See Japanese Patent Laid-open No. 10-305420 for example.
As a device is downsized, the number of devices formed in the wafer is increased to increase the number of streets, which increases the number of laser beam irradiations along the streets. Thus, a laser processing machine is required that can efficiently perform laser processing along streets.